Methods, devices, and materials for metallization

ABSTRACT

A method of making an electronic device which in one embodiment comprises providing a substrate, electrolessly depositing a barrier metal at least on portions of the substrate, and using wet chemistry such as electroless deposition to deposit a substantially gold-free wetting layer having solder wettability onto the barrier metal. An electronic device which in one embodiment comprises a metallization stack. The metallization stack comprises a barrier metal deposited electrolessly and a substantially gold-free wetting layer deposited on the barrier metal, and the wetting layer is wettable by solder.

The present application is a divisional of U.S. patent application Ser.No. 12/832,034, titled “METHODS, DEVICES, AND MATERIALS FORMETALLIZATION,” to KOLICS et al., filed Jul. 7, 2010, projected issuedate Aug. 27, 2013, projected U.S. Pat. No. 8,518,815. U.S. patentapplication Ser. No. 12/832,034 (U.S. Pat. No. 8,518,815) isincorporated herein, in its entirety, by this reference for allpurposes.

BACKGROUND

One or more embodiments of this invention pertain to fabrication ofelectronic devices such as integrated circuits; more specifically, oneor more embodiments of this invention relate to materials andmetallization layers for structures that include solder contacts.

Solder contacts for electrical connections have been in use inelectronic devices for a long time. Numerous established processes existand are in use for fabricating such devices. Many of these processeshave provided satisfactory results and few, if any, major improvementshave been made to many of these established processes.

The present inventors have made one or more discoveries that may bepertinent to solder contact technology such as that for electronicdevices. The one or more discoveries may have the potential to provideone or more methods, materials, and/or electronic devices that involveor use solder contact technology.

SUMMARY

One or more aspects of this invention pertain to fabrication ofelectronic devices. One aspect of the present invention is a method ofmaking an electronic device. According to one embodiment, the methodcomprises providing a substrate, electrolessly depositing a barriermetal at least on portions of the substrate; and using wet chemistrysuch as electroless deposition to deposit a substantially gold-freewetting layer having solder wettability onto the barrier metal.

Another aspect of the present invention is an electronic device.According to one embodiment, the electronic device comprises ametallization stack. The metallization stack comprises a barrier metaldeposited electrolessly and a substantially gold-free wetting layerdeposited on the barrier metal, and the wetting layer is wettable bysolder.

It is to be understood that the invention is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description. The invention iscapable of other embodiments and of being practiced and carried out invarious ways. In addition, it is to be understood that the phraseologyand terminology employed herein are for the purpose of description andshould not be regarded as limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of an embodiment of the presentinvention.

FIG. 2 is a diagram of an embodiment of the present invention.

FIG. 3 is a diagram of an embodiment of the present invention.

FIG. 4 is a diagram of an embodiment of the present invention.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding embodiments of the present invention.

DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification. All numeric values are herein defined as beingmodified by the term “about,” whether or not explicitly indicated. Theterm “about” generally refers to a range of numbers that a person ofordinary skill in the art would consider equivalent to the stated valueto produce substantially the same properties, function, result, etc. Anumerical range indicated by a low value and a high value is defined toinclude all numbers subsumed within the numerical range and allsubranges subsumed within the numerical range. As an example, the range10 to 15 includes, but is not limited to, 10, 10.1, 10.47, 11, 11.75 to12.2, 12.5, 13 to 13.8, 14, 14.025, and 15.

One or more embodiments of the present invention pertain to methods,devices, materials, and/or metallization layers for structures thatinclude solder. More specifically, the present invention is directedtoward materials and metallization layers for electronic devices thatcomprise solder.

Embodiments of the present invention will be discussed below primarilyin the context of processing semiconductor wafers such as silicon wafersused for fabricating electronic devices. The electronic devices includecopper and/or another electrical conductor. The electronic devices haveone or more electrical connections that include solder. However, it isto be understood that embodiments in accordance with the presentinvention may be used for other types of semiconductor devices andwafers other than semiconductor wafers.

Reference is now made to FIG. 1 where there is shown a process flowdiagram 40 according to an embodiment of the present invention. Processflow diagram 40 includes providing a substrate 50. Optionally, thesubstrate may be a substrate such as a semiconductor wafer such as asilicon wafer or a substrate of another material suitable forfabricating electronic devices. Process flow diagram 40 compriseselectrolessly depositing (ELD) a barrier metal 60 at least over portionsof the substrate. Process flow diagram 40 also comprises wet chemicaldeposit such as electrolessly depositing a wetting layer 70. The wettinglayer is a substantially gold-free wetting layer having solderwettability. The wetting layer is deposited on the barrier metal.Optionally, a process flow diagram for an embodiment of the presentinvention may include process flow diagram 40 further comprising formingsolder contacts with the wetting layer.

In process flow diagram 40, the providing a substrate 50 may beaccomplished using a variety of substrates. In other words, a variety ofsubstrates may be used in process flow diagram 40 for additionalembodiments of the present invention. As an option for process flowdiagram 40, the providing a substrate 50 comprises providing a substratecomprising one or more electrical contact pads, and the electrolesslydepositing a barrier metal 60 comprises electrolessly depositing thebarrier metal onto the one or more electrical contact pads.

As another option for process flow diagram 40, the providing a substrate50 comprises providing a substrate comprising one or more throughsubstrate via conductors, and the electrolessly depositing a barriermetal 60 comprises electrolessly depositing the barrier metal onto theone or more through substrate via conductors.

As still another option for process flow diagram 40, the providing asubstrate 50 comprises providing a substrate comprising one or morevias, and the electrolessly depositing a barrier metal 60 compriseselectrolessly depositing the barrier metal onto the walls of the one ormore vias.

Examples of suitable barrier metals for use in process flow diagram 40include, but are not limited to, electrolessly deposited nickel,electrolessly deposited nickel alloy, electrolessly deposited cobalt,and electrolessly deposited cobalt alloy. According to one or moreembodiments of the present invention, process flow diagram 40 comprisesdepositing the barrier metal to a thickness of 0.2 micrometer to 1micrometer and all values and ranges subsumed therein.

For some embodiments of the present invention, the barrier metal iselectrolessly deposited without using palladium or other precious metalsto act as activation metals to initiate the deposition process. Insteadof using palladium or other precious metals for surface activation, oneor more embodiments of the present invention use electroless depositionbaths that comprise reducing agents such as borane for the electrolessdeposition process. The use of borane as at least one of the reducingagents in an electroless deposition bath, according to one or moreembodiments of the present invention may avoid the formation of blackpads that are typically associated with nickel phosphorus barrier layerswith gold wetting layers.

Process flow diagram 40 can be modified for a variety of embodiments ofthe present invention that comprise using one or more options forelectrolessly depositing wetting layer 70. Options for process flowdiagram 40 for electrolessly depositing the wetting layer 70 include,but are not limited to: Electrolessly depositing a substantiallygold-free wetting layer that comprises electrolessly depositing tin or atin alloy. Electrolessly depositing a substantially gold-free wettinglayer that comprises electrolessly depositing silver or a silver alloy.Electrolessly depositing a substantially gold-free wetting layer thatcomprises electrolessly depositing silver tungsten alloy with 3-4 atomicpercent tungsten. Electrolessly depositing a substantially gold-freewetting layer that comprises electrolessly depositing cobalt tin alloy,cobalt copper alloy, cobalt silver alloy, cobalt copper tin alloy,cobalt copper silver alloy, cobalt silver tin alloy, or cobalt coppersilver tin alloy. Electrolessly depositing a substantially gold-freewetting layer that comprises electrolessly depositing nickel copperalloy, nickel silver alloy, nickel copper silver alloy, nickel coppertin alloy, nickel silver tin alloy, or nickel copper silver tin alloy.Electrolessly depositing a substantially gold-free wetting layer thatcomprises electrolessly depositing iron tin alloy, iron copper alloy,iron silver alloy, iron copper tin alloy, iron copper silver alloy, ironsilver tin alloy, or iron copper silver tin alloy. Electrolesslydepositing a substantially gold-free wetting layer that compriseselectrolessly depositing a thickness of nickel alloy having a firstcomposition and a thickness of nickel alloy having a second composition.Electrolessly depositing a substantially gold-free wetting layer thatcomprises electrolessly depositing a thickness of cobalt alloy having afirst composition and a thickness of cobalt alloy having a secondcomposition. Electrolessly depositing a substantially gold-free wettinglayer that comprises electrolessly depositing a thickness of iron alloyhaving a first composition and a thickness of iron alloy having a secondcomposition. Optionally, one or more embodiments of the presentinvention may further comprise incorporating boron and/or phosphorus inthe substantially gold-free wetting layer. For some embodiments of thepresent invention, one or more of the options for electrolesslydepositing a wetting layer 70 may be combined.

For some embodiments of the present invention, process flow diagram 40may further comprise using one or more corrosion prevention procedureson the surface of the wetting layer to keep the surface suitable formaking solder contact. Examples of corrosion prevention procedures thatmay be suitable for embodiments of the present invention include, butare not limited to, depositing a corrosion protective film on thewetting layer; forming an organic solderabily preservative layer;rinsing the wetting layer with a solution containing a corrosioninhibitor; and adjusting the composition of the surface of the wettinglayer so that it is less susceptible to corrosion.

As indicated above, one or more embodiments of the present inventioncomprise using wetting layers in which the composition of the wettinglayer is not constant through the thickness of the wetting layer. Forembodiments of the present invention that comprise electrolesslydepositing a thickness of nickel alloy having a first composition and athickness of nickel alloy having a second composition, the compositionchange can be accomplished by changing one or more deposition conditionssuch as the temperature for the deposition process, and such as thecomposition of the plating formulation. Embodiments of the presentinvention that comprise electrolessly depositing a thickness of cobaltalloy having a first composition and a thickness of cobalt alloy havinga second composition can also use changes in one or more depositionconditions to accomplish the changes in composition of the wettinglayer. Embodiments of the present invention that comprise electrolesslydepositing a thickness of iron alloy having a first composition and athickness of iron alloy having a second composition can also use changesin one or more deposition conditions to accomplish the changes incomposition of the wetting layer.

One or more embodiments of the present invention include methodsaccording to process flow diagram 40 wherein the electrolesslydepositing a barrier metal at least over portions of the substrate 60and the electrolessly depositing a substantially gold-free wetting layer70 having solder wettability are accomplished using an electrolessdeposition bath composition at a temperature T1 to deposit the barriermetal and using the electroless deposition bath composition at anothertemperature T2 to deposit the wetting layer wherein T1 does not equalT2. In other words, T1 and T2 are sufficiently different to causeelectroless deposition of materials having different compositions fromthe same electroless deposition bath composition. Alternatively, theelectrolessly depositing a barrier metal at least over portions of thesubstrate 60 and the electrolessly depositing a substantially gold-freewetting layer 70 having solder wettability are accomplished using anelectroless deposition bath composition over a range of temperatures TR1to deposit the barrier metal and using the electroless deposition bathcomposition over another range of temperatures TR2 to deposit thewetting layer wherein TR1 and TR2 are dissimilar. In other words, TR1and TR2 are sufficiently different to cause electroless deposition ofmaterials having different compositions from the same electrolessdeposition bath composition. For one or more embodiments, the thicknesscomposition profile of the barrier metal may vary as a result of thetemperature variation in TR1 and/or the thickness composition profile ofthe wetting layer may vary as a result of the temperature variation inTR2.

Another embodiment of the present invention includes a method of makingan electronic device. The method comprises providing a substrate 50 thatcomprises providing a substrate that comprises one or more electricalcontact pads and/or one or more through-substrate via conductors. Themethod also comprises electrolessly depositing a barrier metal 60 thatcomprises electrolessly depositing a barrier metal that comprises atleast one of the elements nickel and cobalt. The barrier layer has athickness of 0.2 micrometer to 1 micrometer and all values and rangessubsumed therein at least over portions of the one or more electricalcontact pads and/or the one or more through-substrate via conductors.For electrolessly depositing a wetting layer 70, the method compriseselectrolessly depositing at least one of: tin or a tin alloy; silvertungsten alloy with 3-4 atomic percent tungsten; copper or a copperalloy; cobalt tin alloy; cobalt copper alloy; cobalt silver alloy;cobalt copper tin alloy; cobalt copper silver alloy; cobalt silver tinalloy; cobalt copper silver tin alloy; nickel copper alloy; nickelsilver alloy; nickel copper silver alloy; nickel copper tin alloy;nickel silver tin alloy; nickel copper silver tin alloy; iron tin alloy;iron copper alloy; iron silver alloy; iron copper tin alloy; iron coppersilver alloy; iron silver tin alloy; iron copper silver tin alloy; athickness of nickel alloy having a first composition and a thickness ofnickel alloy having a second composition; a thickness of cobalt alloyhaving a first composition and a thickness of cobalt alloy having asecond composition; and a thickness of iron alloy having a firstcomposition and a thickness of iron alloy having a second composition tocontact the barrier metal so as to form a substantially gold-freewetting layer having solder wettability. Optionally, the method mayfurther comprise incorporating boron and/or phosphorus in thesubstantially gold-free wetting layer. The method also comprises forminga solder contact to the substantially gold-free wetting layer.

Reference is now made to FIG. 2 where there is shown a cross-sectionside view of a part of an electronic device 100 according to oneembodiment of the present invention. Electronic device 100 comprises asubstrate 102 having a base 106, contact pad 110 supported on base 106,and a passivation layer 112 over base 106. Electronic device 100 furthercomprises a metallization stack comprising an electrolessly depositedbarrier metal 114 on electrical contact pad 110 and an electrolesslydeposited substantially gold-free wetting layer 118 on barrier metal114. Wetting layer 118 is wettable by solder. Electronic device 100further includes solder 122 contacting wetting layer 118. FIG. 2 showssolder 122 as a solder ball that may be used for making anotherelectrical contact. FIG. 2 also shows electronic device 100 havingoptional passivation layer 124.

For some embodiments of electronic device 100, substrate 102 maycomprise a completed or partially completed integrated circuit device.Optionally base 106 may be a semiconductor such as silicon or it may beanother material suitable for the fabrication of electronic devices.Optionally, contact pad 110 may comprise a contact pad such as a finalmetal contact pad for electronic devices such as an aluminum contact padand such as a copper contact pad. One or more embodiments of the presentinvention comprise having electrical contact pad 110 at least partiallycovered by barrier metal 114.

One or more embodiments of the present invention include barrier metal114 comprising at least one of the elements nickel and cobalt. Accordingto one embodiment of the present invention, electronic device 100 has athickness of barrier metal 114 that is about 0.2 micrometer to 1micrometer and all values and ranges subsumed therein. For one or moreembodiments of the present invention, barrier metal 114 comprises atleast one of the elements nickel and cobalt and a thickness of thebarrier metal 114 is about 0.2 micrometer to 1 micrometer and all valuesand ranges subsumed therein.

Additional embodiments of the present invention may have wetting layer118 comprising one or more of a variety of materials systems. Examplesof materials systems suitable for use as wetting layer 118 include, butare not limited to: Wetting layer 118 comprising tin or a tin alloy.Wetting layer 118 comprising silver or a silver alloy. Wetting layer 118comprising silver tungsten alloy with 3-4 atomic percent tungsten.Wetting layer 118 comprising copper or a copper alloy. Wetting layer 118comprising cobalt tin alloy, cobalt copper alloy, cobalt silver alloy,cobalt copper tin alloy, cobalt copper silver alloy, cobalt silver tinalloy, or cobalt copper silver tin alloy. Wetting layer 118 comprisingnickel copper alloy, nickel silver alloy, nickel copper silver alloy,nickel copper tin alloy, nickel silver tin alloy, or nickel coppersilver tin alloy. Wetting layer 118 comprising iron tin alloy, ironcopper alloy, iron silver alloy, iron copper tin alloy, iron coppersilver alloy, iron silver tin alloy, or iron copper silver tin alloy.Wetting layer 118 comprising a thickness of nickel alloy having a firstcomposition and a thickness of nickel alloy having a second composition.Wetting layer 118 comprising a thickness of cobalt alloy having a firstcomposition and a thickness of cobalt alloy having a second composition.Wetting layer 118 comprising a thickness of iron alloy having a firstcomposition and a thickness of iron alloy having a second composition.Wetting layer 118 further comprising boron and/or phosphorus.

Reference is now made to FIG. 3 where there is shown a cross-sectionside view of a part of an electronic device 200 according to oneembodiment of the present invention. Electronic device 200 comprises asubstrate 202 having a through-substrate via 210, and athrough-substrate via electrical conductor 212. Electronic device 200also includes a passivation layer 224 over substrate 202. Electronicdevice 200 further comprises a metallization stack comprising anelectrolessly deposited barrier metal 214 on electrical conductor 212and a substantially gold-free wetting layer 218 on barrier metal 214. Asan option, substantially gold-free wetting layer 218 is deposited onbarrier metal 214 electrolessly. Wetting layer 218 is wettable bysolder. Electronic device 200 further includes solder 222 contactingwetting layer 218.

For some embodiments of electronic device 200, substrate 202 maycomprise a completed or partially completed integrated circuit device.Optionally, substrate 202 may be a semiconductor such as silicon or itmay be another material suitable for the fabrication of electronicdevices. Optionally, through-substrate via electrical conductor 212 maycomprise an electrical conductor such as, but not limited to, aluminum,copper, polysilicon, solder, and tungsten. One or more embodiments ofthe present invention comprise having through-substrate via electricalconductor 212 at least partially covered by barrier metal 214.

One or more embodiments of the present invention include barrier metal214 comprising at least one of the elements nickel and cobalt. Accordingto one embodiment of the present invention, electronic device 200 has athickness of barrier metal 214 that is about 0.2 micrometer to 1micrometer and all values and ranges subsumed therein. For one or moreembodiments of the present invention barrier metal 214 comprises atleast one of the elements nickel and cobalt and a thickness of thebarrier metal 214 is about 0.2 micrometer to 1 micrometer and all valuesand ranges subsumed therein.

Additional embodiments of the present invention may have wetting layer218 comprising one or more of a variety of materials systems. Examplesof materials systems suitable for use as wetting layer 218 include, butare not limited to: Wetting layer 218 comprising tin or a tin alloy.Wetting layer 218 comprising silver or a silver alloy. Wetting layer 218comprising silver tungsten alloy with 3-4 atomic percent tungsten.Wetting layer 218 comprising copper or a copper alloy. Wetting layer 218comprising cobalt tin alloy, cobalt copper alloy, cobalt silver alloy,cobalt copper tin alloy, cobalt copper silver alloy, cobalt silver tinalloy, or cobalt copper silver tin alloy. Wetting layer 218 comprisingnickel copper alloy, nickel silver alloy, nickel copper silver alloy,nickel copper tin alloy, nickel silver tin alloy, or nickel coppersilver tin alloy. Wetting layer 218 comprising iron tin alloy, ironcopper alloy, iron silver alloy, iron copper tin alloy, iron coppersilver alloy, iron silver tin alloy, or iron copper silver tin alloy.Wetting layer 218 comprising a thickness of nickel alloy having a firstcomposition and a thickness of nickel alloy having a second composition.Wetting layer 218 comprising a thickness of cobalt alloy having a firstcomposition and a thickness of cobalt alloy having a second composition.Wetting layer 218 comprising a thickness of iron alloy having a firstcomposition and a thickness of iron alloy having a second composition.Wetting layer 218 further comprising boron and/or phosphorus.

Another embodiment of the present invention includes an electronicdevice comprising a metallization stack. The metallization stackcomprises a barrier metal deposited electrolessly and a substantiallygold-free wetting layer deposited electrolessly on the barrier metal.The barrier metal electrically contacts the wetting layer, and thewetting layer is wettable by solder. The barrier metal has a thicknessof 0.2 micrometer to 1 micrometer and all values and ranges subsumedtherein. The barrier metal comprises at least one of the elements nickeland cobalt. The wetting layer comprises: tin or a tin alloy; silver or asilver alloy; silver tungsten alloy with 3-4 atomic percent tungsten;copper or a copper alloy; cobalt tin alloy; cobalt tin alloy includingboron and/or phosphorus; nickel tin alloy; nickel tin alloy includingboron and/or phosphorus; a thickness of nickel tin alloy having a firstcomposition and a thickness of nickel tin alloy having a secondcomposition; or a thickness of cobalt tin alloy having a firstcomposition and a thickness of cobalt tin alloy having a secondcomposition. The electronic device further comprises one or moreelectrical contact pads that are at least partially covered by thebarrier metal and/or one or more through-substrate via conductors thatare at least partially covered by the barrier metal. The embodiment alsocomprises solder contacting the wetting layer.

Reference is now made to FIG. 4 where there is shown a cross-sectionside view of a part of an electronic device 300 according to oneembodiment of the present invention. Electronic device 300 comprises asubstrate 302 having a through-substrate via 310. Electronic device 300further comprises a through-substrate electrical conductor comprising anelectrolessly deposited barrier metal 314 to substantially cover thewalls of through substrate via 310 and a substantially gold-free wettinglayer 318 on barrier metal 314. As an option, substantially gold-freewetting layer 318 is deposited on barrier metal 314 electrolessly.Wetting layer 318 is wettable by solder. Electronic device 300 furtherincludes solder 322 contacting wetting layer 318 to substantially fillthe core enclosed by wetting layer 318. FIG. 4 shows electronic device300 comprising a barrier metal 326 that optionally may have propertiessimilar to barrier metal 314 or may be a dissimilar material. Also, FIG.4 shows electronic device 300 comprising a wetting layer 330 thatoptionally may have properties similar to wetting layer 318 or may be adissimilar material.

For some embodiments of electronic device 300, substrate 302 maycomprise a completed or partially completed integrated circuit device.Optionally substrate 302 may be a semiconductor such as silicon or itmay be another material suitable for the fabrication of electronicdevices. One or more embodiments of the present invention comprisehaving the walls defining through-substrate via 310 at least partiallycovered by barrier metal 314.

One or more embodiments of the present invention include barrier metal314 comprising at least one of the elements nickel and cobalt. Accordingto one embodiment of the present invention, electronic device 300 has athickness of barrier metal 314 that is about 0.2 micrometer to 1micrometer and all values and ranges subsumed therein. For one or moreembodiments of the present invention barrier metal 314 comprises atleast one of the elements nickel and cobalt and the thickness of thebarrier metal 314 is about 0.2 micrometer to 1 micrometer and all valuesand ranges subsumed therein.

Additional embodiments of the present invention may have wetting layer318 comprising one or more of a variety of materials systems. Examplesof materials systems suitable for use as wetting layer 318 include, butare not limited to: Wetting layer 318 comprising tin or a tin alloy.Wetting layer 318 comprising silver or a silver alloy. Wetting layer 318comprising silver tungsten alloy with 3-4 atomic percent tungsten.Wetting layer 318 comprising copper or a copper alloy. Wetting layer 318comprising cobalt tin alloy, cobalt copper alloy, cobalt silver alloy,cobalt copper tin alloy, cobalt copper silver alloy, cobalt silver tinalloy, or cobalt copper silver tin alloy. Wetting layer 318 comprisingnickel copper alloy, nickel silver alloy, nickel copper silver alloy,nickel copper tin alloy, nickel silver tin alloy, or nickel coppersilver tin alloy. Wetting layer 318 comprising iron tin alloy, ironcopper alloy, iron silver alloy, iron copper tin alloy, iron coppersilver alloy, iron silver tin alloy, or iron copper silver tin alloy.Wetting layer 318 comprising a thickness of nickel alloy having a firstcomposition and a thickness of nickel alloy having a second composition.Wetting layer 318 comprising a thickness of cobalt alloy having a firstcomposition and a thickness of cobalt alloy having a second composition.Wetting layer 318 comprising a thickness of iron alloy having a firstcomposition and a thickness of iron alloy having a second composition.Wetting layer 318 further comprising boron and/or phosphorus.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the present invention as set forthin the claims below. Accordingly, the specification is to be regarded inan illustrative rather than a restrictive sense, and all suchmodifications are intended to be included within the scope of thepresent invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having,” “at least one of,” or any other variationthereof, are intended to cover a non-exclusive inclusion. For example, aprocess, method, article, or apparatus that comprises a list of elementsis not necessarily limited only to those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

What is claimed is:
 1. A method of making an electronic device, themethod comprising: providing a substrate; electrolessly depositing abarrier metal at least over portions of the substrate; and electrolesslydepositing a substantially gold-free wetting layer having solderwettability onto the barrier metal; wherein the providing a substratecomprises providing a substrate comprising one or more through-substratevia conductors and wherein the electrolessly depositing the barriermetal at least over portions of the substrate comprises depositing thebarrier metal onto the one or more through-substrate via conductors. 2.A method of making an electronic device, the method comprising:providing a substrate; electrolessly depositing a barrier metal at leastover portions of the substrate; and electrolessly depositing asubstantially gold-free wetting layer having solder wettability onto thebarrier metal; wherein the providing a substrate comprises providing asubstrate having one or more vias and wherein the electrolesslydepositing the barrier metal at least over portions of the substratecomprises depositing the barrier metal onto the walls of the one or morevias.
 3. An electronic device comprising a metallization stack, themetallization stack comprising a barrier metal deposited electrolesslyand a substantially gold-free wetting layer deposited electrolessly, thebarrier metal contacting the wetting layer, and the wetting layer beingwettable by solder.
 4. The electronic device of claim 3, furthercomprising electrical contact pads at least partially covered by thebarrier metal.
 5. The electronic device of claim 3, further comprising athrough-substrate via conductor at least partially covered by thebarrier metal.
 6. The electronic device of claim 3, wherein thesubstrate has one or more through-substrate vias, the walls of thesubstrate forming the one or more vias are at least partially covered bythe barrier metal and further comprising solder contacting the wettinglayer to substantially fill the one or more vias.
 7. The electronicdevice of claim 3, wherein the barrier metal has a thickness of 0.2micrometer to 1 micrometer and all values and ranges subsumed therein.8. The electronic device of claim 3, wherein the barrier metal comprisescobalt.
 9. The electronic device of claim 3, wherein the wetting layercomprises tin or a tin alloy.
 10. The electronic device of claim 3,wherein the wetting layer comprises silver tungsten alloy with 3-4atomic percent tungsten.
 11. The electronic device of claim 3, whereinthe wetting layer comprises cobalt tin alloy, cobalt copper alloy,cobalt silver alloy, cobalt copper tin alloy, cobalt copper silveralloy, cobalt silver tin alloy, or cobalt copper silver tin alloy. 12.The electronic device of claim 11, wherein the wetting layer furthercomprises boron and/or phosphorus.
 13. The electronic device of claim 3,wherein the wetting layer comprises nickel copper alloy, nickel silveralloy, nickel copper silver alloy, nickel copper tin alloy, nickelsilver tin alloy, or nickel copper silver tin alloy.
 14. The electronicdevice of claim 13, wherein the wetting layer further comprises boronand/or phosphorus.
 15. The electronic device of claim 3, wherein thewetting layer comprises iron tin alloy, iron copper alloy, iron silveralloy, iron copper tin alloy, iron copper silver alloy, iron silver tinalloy, or iron copper silver tin alloy.
 16. The electronic device ofclaim 15, wherein the wetting layer further comprises boron and/orphosphorus.
 17. The electronic device of claim 3, wherein the wettinglayer comprises a thickness of nickel tin alloy having a firstcomposition and a thickness of nickel tin alloy having a secondcomposition.
 18. The electronic device of claim 3, wherein the wettinglayer comprises a thickness of cobalt tin alloy having a firstcomposition and a thickness of cobalt tin alloy having a secondcomposition.
 19. The electronic device of claim 3, wherein the barriermetal has a thickness of 0.2 micrometer to 1 micrometer and all valuesand ranges subsumed therein, the barrier metal comprises at least one ofthe elements nickel and cobalt; wherein the wetting layer comprises: 1.tin or a tin alloy;
 2. silver tungsten alloy with 3-4 atomic percenttungsten;
 3. cobalt tin alloy, cobalt copper alloy, cobalt silver alloy,cobalt copper tin alloy, cobalt copper silver alloy, cobalt silver tinalloy, or cobalt copper silver tin alloy;
 4. nickel copper alloy, nickelsilver alloy, nickel copper silver alloy, nickel copper tin alloy,nickel silver tin alloy, or nickel copper silver tin alloy;
 5. iron tinalloy, iron copper alloy, iron silver alloy, iron copper tin alloy, ironcopper silver alloy, iron silver tin alloy, or iron copper silver tinalloy;
 6. a thickness of nickel alloy having a first composition and athickness of nickel alloy having a second composition;
 7. a thickness ofcobalt alloy having a first composition and a thickness of cobalt alloyhaving a second composition; or
 8. a thickness of iron alloy having afirst composition and a thickness of iron alloy having a secondcomposition; further comprising one or more electrical contact padsbeing at least partially covered by the barrier metal and/or one or morethrough-substrate via conductors being at least partially covered by thebarrier metal; and solder contacting the wetting layer.